1. Technical Field
The present application relates to a system for mixing hazardous materials, and more particularly, to a closed system for mixing hazardous materials such as bone cement.
2. Background Information
Many substances in common use in industry and other fields are known to have toxic and/or noxious properties. To the extent possible, efforts are generally made to attempt to minimize human exposure to such substances. However, appropriate standards are not always available to evaluate the extent to which such substances may be safely used. In addition, accurate means to determine the amount of the substance in a defined space are not always available. Over-exposure to hazardous substances can have severe health consequences to the exposed person. It can also result in legal consequences to a manufacturer and/or seller of such substances, as well as to an employer of the exposed person. Thus, there is an ongoing need for improved techniques and apparatus to minimize unnecessary exposure to hazardous substances.
One substance known to be hazardous to living organisms is the liquid monomer methyl methacrylate. Methyl methacrylate is in widespread use in industry, and particularly in the medical and dental industries, where it is a component of bone cement. Methyl methacrylate is highly volatile and flammable, and is intended for use only in areas provided with adequate air circulation and ventilation. Excessive exposure to this liquid monomer has been implicated in conditions such as contact dermatitis, asthma, drowsiness, headaches, anorexia, sexual disorders, decrease in gastric motor activity, and irritation of the respiratory tract and eyes, among other conditions. Particularly severe conditions that have been reported include pregnancy complications, and disorders of the liver. Accordingly, many products containing methyl methacrylate, such as bone cements, are regulated in the United States by the Food and Drug Administration, and in numerous other countries by the appropriate regulatory bodies.
Bone cement is generally sold as two separately packaged components. One of the components is a liquid, and the other component is a powder. The liquid component primarily comprises the liquid monomer methyl methacrylate (MMA), and may also include a polymerization inhibitor, such as hydroquinone, and an accelerator, such as dimethyl para-toluidine. The powder component primarily comprises polymethyl methacrylate (PMMA), and may also include an initiator for the polymerization reaction of MMA to PMMA, such as dibenzoyl peroxide, and a radiopaque substance, such as barium sulfate, to assist in the identification of the bone cement under fluoroscopy.
During preparation of bone cement, the liquid component is mixed with the powder component. During this reaction, harmful methyl methacrylate vapors are released. Attempts have been made to minimize the effect of these vapors, such as performing the transfer in an exhaust hood, or in a closed system such as a vacuum. Although these techniques are preferable to carrying out the mixing operation in an open room environment, the techniques are not without shortcomings. For example, each technique necessitates that the transfer take place in a room that is specially equipped with the necessary equipment, such as an exhaust hood or a vacuum generator. Although the use of an exhaust hood can eliminate a high percentage of the vapors, exhaust hoods have varying degrees of reliability, and some vapors can nevertheless escape. Even small amounts of released vapors in a room environment can adversely affect sensitive persons. The use of a vacuum is generally effective in controlling such vapors, however vacuum apparatus can be complicated and difficult to operate.
Accordingly, it is desired to provide a system for mixing hazardous substances, such as bone cement, that minimizes excessive exposure to the hazardous substances. In addition, it is desired to provide a system that utilizes readily accessible components, is easy to operate, and is inexpensive.